The present disclosure relates to a concentrating solar energy system with a reflector having a specularly reflecting inner side realized as a parabolic mirror with two axis steering which is carried by a base frame arranged in a support plane and with a receiver which is arranged in operation at, in front of or after the focal point of the parabolic mirror, wherein the parabolic mirror is moreover rotatable about an axis arranged substantially perpendicular to the support plane.
The solar energy installations which have previously been realized can be roughly divided into three groups: photovoltaic installations, which produce electrical current directly from sunlight, solar collectors which take up heat from sunlight areally and concentrating solar energy systems which strongly bundle the sunlight and are able to recover high-temperature energy in a receiver. The concentrating solar energy systems are physically characterised in that the energy can be exploited at a plurality of levels. In this way, efficiencies of over 70% can be achieved. For example, if heat is produced at 600° C. then this can be exploited in the range from 600° C. to 100° C. for the generation of electrical current. The waste heat which arises can then be used in the form of hot water at ca. 90° C.
These concentrating systems have the disadvantage that they have to be steered to follow the sun, which can be very complicated with large areas. Three different types of concentrating solar energy systems can be distinguished: solar tower power stations in which the steering to follow the sun takes place with the aid of heliostats, parabolic channel systems which only have to be steered to follow the sun vertically and parabolic reflectors with two-axis steering.
Suggestions for the realization of solar energy installations and also for the possibility of using Stirling engines, which can be used amongst other things as a drive for power generators, as well as possibilities of storing energy, are described in the book “Stirlingmaschinen—Grundlagen. Technik. Anwendung by Martin Werdich ISBN 3-922964.35-(4” (Stirling engines-principles. Technology. Utilisation) The book shows in FIG. 53 a parabolic reflector with two-axis steering which is circular in plan view and is carried by a complicated base frame and a framework mounted thereon. The parabolic mirror is supported in space facing the sun and is pivotable about a horizontal axis which is located parallel to a diameter of the parabolic mirror, which is circularly round in plan view, in front of its specularly reflecting surface in order to enable vertical steering in accordance with the vertical position of the sun. This vertical steering is termed elevational steering or height steering in specialist language. Moreover, a rotation of the parabolic mirror about an axis perpendicular to the base frame is possible. This rotation brings about the horizontal steering to follow the sun.
A similar construction is known from the German utility model G 8427130.2. There, a part paraboloid is used as a reflector in place of a full paraboloid and extends over approximately 240° around the axis of symmetry of the paraboloid. Here, the vertical steering takes place about a pivot axis which is fixedly arranged at the base frame, and indeed at a significant height above the base frame.
Problematic with this known construction is above all the arrangement of the horizontal axis which serves for the vertical steering to follow the sun.
Problems arise with this arrangement in that the parabolic reflector must be arranged so high above the ground that sufficient ground clearance exists for the vertical steering. The center of gravity of the system thus lies at a very high position.
In large systems, in which the diameter of the parabolic reflector amounts to 10 m–20 m, this leads to very massive embodiments weighing tons, because the construction must also be storm-proof.
With this construction the sensitive reflector surface cannot be simply protected against environmental effects, such as precipitation. In this way, a considerable cleaning effort arises which also leads to increased wear of the reflector surface. Soft, favorably priced materials, such as reflecting plastic foils, cannot be used for the reflector layer. The mirror would become prematurely dull.
Furthermore, it is completely inconceivable to place a system of this kind on the flat roof of a normal building, because it is too heavy and would project too far above the house. The roof of a house is, however, actually the most favorable position for the installation of solar energy systems, because there is little shade here and the otherwise unused surface can be exploited. Furthermore, the energy transport path is very short, i.e. the system is suitable for decentral energy supply.